Cannister or tank type vacuum cleaners are used for collecting various types of material, both dry and wet, and they are sometimes even used for collecting water or other liquids.
In a typical cannister or tank vacuum cleaner, the tank has a lid over it and the vacuum cleaner motor is supported on the lid. The vacuum cleaner motor drives an impeller fan. The fan has an inlet side that communicates into the tank and draws a vacuum there.
In the usual cannister vacuum cleaner, the lid is a separate disc or plate that is attached and perhaps clamped over the open top of the cannister. The lid is typically a flat surfaced disc. To provide the lid with the strength needed for supporting the motor, especially while it is in operation, and for supporting the filter assembly, the lid is typically formed of a strong, relatively rigid metal disc. The periphery of the disc is shaped to sealingly engage the upper end of the side walls of the tank. A hole is cut through the lid just beneath the mounting for the motor and this hole provides communication between the interior of the tank and the impeller fan driven by the motor.
A filter assembly is interposed between the interior of the tank and the inlet to the impeller fan for capturing particulate matter so that it does not escape into and past the fan and is not expelled from the vacuum cleaner. In the typical tank vacuum cleaner, directly beneath the lid of the tank and at the inlet to the impeller fan, there is a filter support for supporting a replaceable filter element. Typically, the filter support is in the form of a filter cage which is generally cylindrically shaped, and the filter element is in the form of a cylindrical annulus which is removably press fit over the filter cage. The annular sides of the filter cage are defined by vertical ribs, shaped and placed to support the surrounding filter element, yet spaced apart so as not to interfere with air flow. The bottom of the filter cage is closed off.
In situations where liquid or wet materials are being collected, it is necessary that the flow out of the tank and into the vacuum cleaner motor be halted before the liquid or wet material is drawn into the motor.
For supporting the particulate material filter element, the filter cage of the typical cannister vacuum cleaner is secured to the underside of the lid around the hole through the lid. Typically, the filter cage is a molded plastic unit with an annular collar at its upper edge. This collar is bolted to the underside of the lid. The separate formation of the lid and filter cage and the later attachment together of these elements necessitates separate formation and attachment procedures, which it would be desirable to eliminate or reduce.
Inside the filter cage, there is a float element that sits on the base of the filter cage and that is adapted to float up through the filter cage once the level of liquid in the tank rises above the bottom of the filter cage. The float element comprises a freely floating ball or cylinder. The float element eventually floats up high enough to seal the inlet to the impeller fan. Further operation of the vacuum cleaner is blocked until the tank is emptied of collected material. At the same time, the filter element may also be replaced.
The bottom end of the filter cage is closed off by a bottom cover. A separate inlet grid element is attached across the hole through the tank lid for permitting air to pass through the hole in the lid while also enclosing the top end of the filter cage.